Posted on Sep 22, 2012

This simple circuit can convert a single supply voltage, such as a battery, into a bipolar supply. Sense resistors Rl and R2 establish relative magnitudes for the resulting positive and negative voltages. Their rail-to-rail value, of course, equals VsUPPLY· R4 and R5 represent the load impedances. For example, equalvalue sense resistors produce 1/z VsvPPLY across each of the load resistors, R4 and R5.

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The op amp maintains these equal voltages by sinking or sourcing current through R3; the op amp"s action is equivalent to that of variable conductances Gland G2 in shunt with each load resistor. Choose a value for R3 so that the largest voltage across it, the greatest load-current mismatch, won"t exceed the op amp"s output-voltage capability for the application. You can add a buffer amplifier at the op amp"soutput to provide greater load currents. Ifyou need bypass capacitors across the load resistors as well, connect a capacitor (dashed lines) to ensure that the amplifier remains stable.

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